Tubing rotator

ABSTRACT

A tubing rotator  10  rotatably suspending a tubing string TS in a well having a wellhead W includes a tubing hanger  12  for supporting the tubing string, and a mandrel  14  having a bore therein and connected to the tubing string. A coupling sleeve  30  rotatably connects the mandrel to the rotator drive shaft  16,  and transfers rotational energy from the drive shaft to the mandrel while allowing for the disengagement of the coupling sleeve from the mandrel in a direction substantially parallel to a longitudinal axis of the mandrel. The coupling sleeve has interior surfaces  70  for mating with an exterior surfaces  72  on the mandrel, with each surface having a substantially curvilinear configuration about its circumference defining a plurality of curved radially outward extending peaks and curved radially inward extending valleys.

FIELD OF THE INVENTION

This invention relates to a tubing rotator for rotatably hanging a tubing string in a wellhead. More particularly, the invention relates to improvements in the interconnection between the mandrel and a coupling sleeve to transfer rotational energy to the mandrel while allowing for the disengagement of the coupling sleeve from the mandrel in a direction substantially parallel to a longitudinal axis of the mandrel.

BACKGROUND OF THE INVENTION

Various types of tubing rotators have been devised to slowly rotate a tubing string and thereby more evenly distribute wear around the inside circumference of the tubing string. In many applications, the sucker rod and/or guides on the sucker rod come into contact with the inner surface of a tubing string, thereby creating a potential leak path from the tubing string. Tubing rotators have been widely used to extend the life of the tubing. Various tubing rotators are disclosed in U.S. Pat. Nos. 5,383,519, 5,427,178 and 6,026,898.

A significant improvement in tubing rotators allow the operator to lift a coupling sleeve from a mandrel in a direction substantially parallel to a longitudinal axis of the mandrel. This allows the tubing hanger to hang or support the tubing string in the well while allowing the coupling sleeve and the rotator drive shaft to be removed from the wellhead without having to lift the tubing string from the well. U.S. Pat. No. 5,465,788 discloses a tubing rotator with a large number of splines interconnecting the mandrel and the coupling sleeve. U.S. Pat. No. 6,543,533 discloses a tubing rotator with a hex-shaped connection between the mandrel connected to the tubing string and the coupling sleeve rotatably connecting the mandrel to the rotator drive shaft.

Prior art tubing rotators desirably are highly reliable, can be manufactured at a relatively low cost, and provide a long life with relatively little service. The tubing rotator of the present invention improves these qualities of a tubing rotator, and overcomes the disadvantages of the prior art.

SUMMARY OF THE INVENTION

In one embodiment, the tubing rotator for rotatably suspending a tubing string on a wellhead includes a tubing hanger for engagement with a wellhead to support the tubular string, and a mandrel within the tubing hanger having a bore therein and connected to the tubing string. A coupling sleeve rotatably connects the mandrel to a rotator drive shaft, which may have an axis perpendicular to the axis of the coupling sleeve. The coupling sleeve transfers rotational energy from the drive shaft to the mandrel while allowing for the disengagement of the coupling sleeve from the mandrel in a direction substantially parallel to a longitudinal axis of the mandrel. The coupling sleeve has an interior surface for mating with an exterior surface on the mandrel, and each surface has a substantially curvilinear configuration about its circumference and defines a plurality of curved radially outward extending peaks and curved radially inward extending valleys.

These and further features and advantages of the present invention will become apparent from the following detailed description, wherein reference is made to the figures in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view of an upper portion of a wellhead and a tubing rotator for rotatably suspending a tubing string in a well.

FIG. 2 is a cross-sectional view of the rotator shown in FIG. 1.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 depicts a tubing rotator 10 including a tubing hanger 12, a mandrel 14, a rotator body or housing 64, and rotator drive shaft 16.

A tubing hanger 12 has a tapered lower surface for engagement with a mating surface on the wellhead W. A plurality of seals 20 seal between the tubing hanger and the wellhead. A mandrel 14 is rotatably mounted within the tubing hanger 12, with bearing 22 facilitating rotation. The lower end of the mandrel 14 includes thread 24 for interconnection with threads on the tubing string TS. At its upper end, the mandrel 14 includes threads 26 on its interior bore to serve as pickup threads when the tubing string TS is lifted from the wellhead W.

Mandrel 14 is rotatably coupled to coupling sleeve 30, which in turn is mechanically coupled to the rotator drive shaft 16. The mandrel 14 is supported on the tubing hanger 12. An upper portion of the mandrel is positioned within the rotator housing 64, while a lower portion is within the wellhead W. Coupling sleeve 30 may be sealed to the body 14 by seal 28, and may be sealed to the mandrel by seal 32. The mandrel 14 may be sealed to the tubing hanger 12 by seals 33. Bolts or other securing members 15 may mechanically interconnect the housing 64 to the wellhead W, with seal 31 providing a fluid-tight seal between these housings. A conventional grease fitting 34 plugs a passageway 36 in the housing 64 which is in communication with the exterior surface of the sleeve 30, and a similar grease fitting 38 in the passageway 40 in the housing 64 is in communication with the rotator drive shaft 16. The pickup threads 26 allow the mandrel and the tubing string to be lifted from the wellhead by threading a shaft or pipe to the pickup threads.

The rotator of the present invention allows for disengagement of the tubing hanger from the mandrel through the application of force, and through movement, in a direction substantially parallel to a longitudinal axis of the tubing string. The rotator provides for the rotational movement of a mandrel while facilitating the removal of tubing rotator when lifting it off the wellhead without significant rotational movement and without running the risk of loosening threaded joints in the tubing string.

The mandrel 14 has a longitudinal central axis 15, which is substantially coaxial with a central axis of both the coupling sleeve 30 and the tubing string TS. In a preferred embodiment, the drive gear is a worm gear having worm gear teeth for engagement with the coupling sleeve.

Referring now to FIG. 2, the rotator drive shaft 16 has external teeth 42 for mating with external teeth 44 on a coupling sleeve 30. The drive gear 16 has an axis of rotation 17 substantially perpendicular and spaced from the axis 15 of the mandrel. An end cap 46 may rotatably support an end of the rotator drive shaft 16, with bearings 48 and ring 50 held within the housing 64 by snap ring 52. The power end 54 of the worm gear 16 may be rotated by various types of power drives, including an electric motor and a hydrocarbon fueled engine. Cutouts 56 and 58 in the housing 64 may be provided for receiving the grease fittings discussed above.

FIG. 2 depicts the mandrel 14 having a bore 17 therein, and positioned within the coupling sleeve 30 which is driven by the drive shaft 16. The coupling sleeve 30 thus rotatably connects the mandrel 14 to the drive shaft 16 by transferring rotational energy from the drive shaft to the mandrel. More specifically, the coupling sleeve 30 has an interior surface 70 for mating with the exterior surface 72 on the mandrel, with each surface having a substantially curvilinear configuration about its circumference. The interior surface on the coupling sleeve and the exterior surface on the mandrel each define a plurality of curved radially outward extending peaks and curved radially inward extending valleys. Each curved peak and valley may lie along a surface which is substantially parallel to axis 15, as shown in FIG. 1. This interconnection allows for the disengagement of the coupling sleeve from the mandrel in a direction substantially parallel to a longitudinal axis of the mandrel. The number of peaks and valleys in these mating surfaces which are circumferentially positioned about the circumference of the coupling sleeve in the mandrel is not critical. A large number of circumferential mating surfaces generally require more machining costs than a smaller number of mating surfaces. From four to ten peaks and valleys may extend circumferentially about the coupling sleeve 30 and the mandrel 14. By avoiding the use of surfaces with planar sides, the radial spacing between a valley on the mandrel and the bore of the mandrel, and between a valley on the coupling sleeve and the exterior surface of a coupling sleeve, may be minimized. This results in a more robust tubing rotator, and/or a rotator or a rotator body with the selected smaller radial spacing for receiving the outermost diameter of the coupling sleeve. Also, by minimizing sharp corners, the strength of the mandrel and coupling sleeve are enhanced.

It should be understood that while each of the surfaces 70 and 72 have a substantially curvilinear configuration about its circumference, the peak in the coupling sleeve 30 between two valleys may have a short section which is also curvilinear, but alternatively could have one or more straight sides. It is, however, the plurality of curved radially outwardly extending peaks and curved radially inward extending valleys on the coupling sleeve 30 and the mandrel 14 which transmit rotational energy from the drive shaft 16 to the mandrel 14.

The exterior surface of the coupling sleeve and the internal surface of the mandrel may extend axially in a direction substantially parallel to the longitudinal axis of the mandrel. This allows the coupling sleeve to be lifted vertically from the mandrel in a straight upward direction substantially parallel to a longitudinal axis of the mandrel. In other embodiments, the peaks and valleys in these surfaces could be arranged along a slight spiral, such that the coupling sleeve would disengage from the mandrel while pulling upward and rotating the coupling sleeve from the mandrel.

According to the method of the invention, the tubing hanger is engaged with the wellhead for supporting the tubing string. The mandrel having a bore therein is connected to the tubing string, and a coupling sleeve rotatably connects the mandrel to a rotator drive shaft to transfer rotational energy from the drive shaft to the mandrel while allowing for the disengagement of the coupling sleeve from the mandrel in a direction substantially parallel to a longitudinal axis of the mandrel. The coupling sleeve is provided with an exterior surface for mating with an interior surface of the mandrel, with each surface having a substantially curvilinear configuration about its circumference and defining a plurality of curved radially outward extending peaks and curved radially inward extending valleys.

Each of the curvilinear surfaces on the mandrel and on the coupling sleeve may have a substantially sinusoidal configuration with respect to the axis of the mandrel. Moving circumferentially, the curvilinear peaks and valleys provide a radial spacing of the force transfer surfaces on the coupling sleeve 30 and the mandrel 14 to the axis of the mandrel which varies sinusoidally.

Although specific embodiments of the invention have been described herein in some detail, this has been done solely for th purposes of explaining the various aspects of the invention, and is not intended to limit the scope of the invention as defined in the claims which follow. Those skilled in the art will understand that the embodiment shown and described is exemplary, and various other substitutions, alterations and modifications, including but not limited to those design alternatives specifically discussed herein, may be made in the practice of the invention without departing from its scope. 

1. A tubing rotator for rotatably suspending a tubing string in a well having a wellhead, the tubing rotator comprising: a tubing hanger for engagement with the wellhead and supporting the tubing string; a mandrel having a bore therein and connected to the tubing string; a coupling sleeve rotatably connecting the mandrel to a rotator drive shaft, the coupling sleeve transferring rotational energy from the drive shaft to the mandrel while allowing for the disengagement of the coupling sleeve from the mandrel in a direction substantially parallel to a longitudinal axis of the mandrel; and the coupling sleeve having an interior surface for mating with an exterior surface on the mandrel, each surface having a substantially curvilinear configuration about its circumference and defining a plurality of curved radially outward extending peaks and curved radially inward extending valleys.
 2. A tubing rotator as defined in claim 1, wherein each of the curvilinear surfaces on the mandrel and on the coupling sleeve have a substantially sinusoidal configuration with respect to the axis of the mandrel.
 3. A tubing rotator as defined in claim 1, further comprising: a bearing between the tubing hanger and the mandrel to facilitate rotation of the mandrel within the tubing hanger.
 4. A tubing rotator as defined in claim 1, further comprising: a first seal between the tubing hanger and the wellhead, and a second seal between the tubing hanger and the mandrel.
 5. A tubing rotator as defined in claim 1, further comprising: an upper portion of said mandrel including internal tubing string pickup threads.
 6. A tubing rotator as defined in claim 1, further comprising: a tubing rotator housing mounted on the wellhead; and a portion of the mandrel is positioned within a wellhead and a portion of the mandrel is positioned within the tubing rotator housing.
 7. A tubing hanger as defined in claim 1, wherein the interior surface on the coupling sleeve and the exterior surface on the mandrel extend axially in a direction substantially parallel to the longitudinal axis of the mandrel.
 8. A tubing rotator as defined in claim 1, wherein the drive gear is a worm gear having worm gear teeth for engagement with the coupling sleeve.
 9. A tubing rotator is defined in claim 1, wherein the tubing hanger has a tapered exterior surface for engaging a tapered interior surface on the wellhead for supporting the tubing hanger.
 10. A tubing rotator as defined in claim 1, wherein a lower end of said mandrel includes threads for threaded engagement with the tubing string.
 11. A tubing rotator for rotatably suspending a tubing string in a well having a wellhead, the tubing rotator comprising: a tubing hanger for engagement with the wellhead and supporting the tubing string; a mandrel having a bore therein and connected to the tubing string and supported on the tubing hanger; a coupling sleeve rotatably connecting the mandrel to a rotator drive shaft, the coupling sleeve transferring rotational energy from the drive shaft to the mandrel while allowing for the disengagement of the coupling sleeve from the mandrel in a direction parallel to a longitudinal axis of the mandrel; the coupling sleeve having an interior surface for mating with an exterior surface on the mandrel, each surface having a substantially curvilinear configuration about its circumference and defining a plurality of curved radially outward extending peaks and curved radially inward extending valleys; each of the curvilinear surfaces on the mandrel and on the coupling sleeve have a substantially sinusoidal configuration with respect to the axis of the mandrel; and a bearing between the tubing hanger and the mandrel to facilitate rotation of the mandrel within the tubing hanger.
 12. A tubing rotator as defined in claim 11, further comprising: a first seal between the tubing hanger and the wellhead, and a second seal between the tubing hanger and the mandrel.
 13. A tubing hanger as defined in claim 11, wherein the exterior surface on the coupling sleeve and the interior surface on the mandrel extend axially in a direction substantially parallel to the longitudinal axis of the mandrel.
 14. A tubing rotator as defined in claim 11, further comprising: a tubing rotator housing mounted on the wellhead; and a portion of the mandrel is positioned within a wellhead and a portion of the mandrel is positioned within the tubing rotator housing.
 15. A tubing rotator as defined in claim 11, wherein the drive gear is a worm gear having worm gear teeth for engagement with the mandrel.
 16. A method of rotatably suspending a tubing string in a well having a wellhead, the method comprising: engaging a tubing hanger with the wellhead for supporting the tubing string; connecting a mandrel having a bore therein with the tubing string; rotatably connecting a coupling sleeve between the mandrel and a rotator drive shaft, the coupling sleeve transferring rotational energy from the drive shaft to the mandrel while allowing for the disengagement of the coupling sleeve from the mandrel in a direction substantially parallel to a longitudinal axis of the mandrel; and providing the coupling sleeve with an interior surface for mating with an exterior surface on the mandrel, each surface having a substantially curvilinear configuration about its circumference and defining a plurality of curved radially outward extending peaks and curved radially inward extending valleys.
 17. A method as defined in claim 16, wherein each of the curvilinear surfaces on the mandrel and on the coupling sleeve have a substantially sinusoidal configuration with respect to the axis of the mandrel.
 18. A method as defined in claim 16, further comprising: providing an upper portion of said mandrel with internal tubing string pickup threads; and lifting the tubular string from the pickup threads.
 19. A method as defined in claim 16, further comprising: providing a first seal between the tubing hanger and the wellhead; and providing a second seal between the tubing hanger and the mandrel.
 20. A method as defined in claim 16, further comprising: providing a bearing between the tubing hanger and the mandrel to facilitate rotation of the mandrel within the tubing hanger. 